1. Field of the Invention
The present invention relates to a bookbinding system, a bookbinding method, a computer program product, and a punched hole detecting device.
2. Description of the Related Art
Among various functions, which are included in a post-processor of an existing image forming apparatus, the post-processor includes a function in which multiple holes are punched sheet by sheet on a binding-side end portion of a sheet, sheets are arranged by a page order, and each copy is loaded onto a sheet discharge tray. An output material thus obtained is bound by a metallic coil or a plastic ring by using an off-line device or a tool. A ring-bound material is formed with this process.
A sheet processing system is known in which a plurality of operating devices such as a punch processing device and a staple processing device are connected to the image forming apparatus in a line (in a series). The punch processing device and the staple processing device execute a punching process and a stapling process with respect to the sheet on which an image is formed by the image forming apparatus. Thus, a sheet or a sheet stack is created on which a desired sheet processing is carried out.
Functions related to a bookbinding process includes a function that binds the sheet on the end portion or in a center, a function that carries out bookbinding by pressing a sheet edge on a self-adhesive tape, and a function that binds, upon punching a plurality of holes near the binding-side of the sheet stack, the sheet stack using the metallic coil or the plastic ring to form the ring-bound material. In recent years, an inline executable ring binder device has also appeared for ring binding in which the sheet stack is bound by passing the metallic coil or the plastic ring through the holes that are punched near the binding-side of the sheet stack, thus significantly increasing productivity.
A technology disclosed in Japanese Patent Application Laid-open No. 2005-138549 is a commonly known example of the technology related to such a ring binder device. In the technology mentioned earlier, a binding processor includes a punching mechanism and a binding processing mechanism that executes a binding process using binders. When a sheet from a printing device such as a copier is transmitted, the sheet strikes a stopper plate of the punching mechanism. A sheet aligning slider clamps a left and a right side of the sheet and positions the sheet. After the holes are punched by a punch block and a die, the sheet is sent to a sheet tray of the binding processing mechanism. By arranging a single set of the sheets and sandwiched pressuring ring-type binders by using a pusher, the ring-type binders are mounted into the punching holes of the sheet and a binding processed booklet is discharged in a stack tray.
A binder device, which executes the binding process according to the technology mentioned earlier, includes a multi-hole punching device. When ring binding is to be carried out, the multi-hole punching device punches multiple holes on all the sheets subjected to the binding process after the sheets are output from the image forming apparatus. Subsequently, by aligning all the sheets, the binder device executes the binding process. The multi-hole punching device, which is included in a bookbinding system or the binder device, is formed by assuming punching on a single sheet of a general thickness. For example, punching cannot be carried out on a heavy sheet or a plastic film, thus restricting creation of a ring bound booklet. If the booklet, which is punched and subjected to the binding process, is separated, the sheets of the booklet are fed from an inserter, and the booklet is to be restructured by performing changes, the holes need to be punched again, thus resulting in displacement and widening of the holes.